A PROSPECTIVE-STUDY OF CALCIUM-METABOLISM IN EXERTIONAL HEAT-STROKE WITH RHABDOMYOLYSIS AND ACUTE-RENAL-FAILURE

Intensive training in a humid and warm environment can cause exertiona l heat stroke (ExHS) and rhabdomolysis (RED) in military recruits. To investigate the role of vitamin D and monomeric calcitonin (CT) on the calcium metabolism in ExHS with RED and acute renal failure (ARF), we studied 21 recruits with ExHS (mean age 21.4 years), 7 of which had A RF. Another 11 age-matched recruits with heat exhaustion (HE) and 11 h ealthy subjects were selected as controls. Our results showed that in 14 ExHS patients without ARF, mean serum creatinine (Cr) levels were s ignificantly higher(151.16 vs. 106.08 mu mol/l, p < 0.01), whereas ser um osteocalcin (OC) levels were significantly lower (2.22 vs. 4.65 mu g/l, p < 0.01) than in healthy controls, In 7 patients with ExHS and A RF, the mean serum Cr (774.38 vs. 105.20 mu mol/l, p < 0.01), phosphor us (P) (2.26 vs. 1.26 mmol/l, p < 0.05), creatine phosphokinase (CPK) 274,143.97 vs. 85.78 IU/l, p < 0.05), intact parathyroid hormone (I-PT H) (299.81 vs. 18.66 ng/l, p < 0.05) and CT (13.58 vs. 6.63 ng/l, p < 0.01) levels on admission were significantly higher while the mean ion ized calcium (iCa) levels were significantly lower than the healthy co ntrols (0.9 vs. 1.18 mmol/l, p < 0.01). The mean serum 25-hydroxyvitam in D [25(OH)D] levels were not significantly different from healthy co ntrols. However, mean serum 1,25-dihydroxyvitamin D [1,25(OH)(2)D] lev els and the ratio of 1,25(OH)(2)D to 25(OH)D were significantly lower than healthy controls throughout the whole course of ARF. None of the 7 patients with ExHS and ARF developed hypercalcemia during the diuret ic phase. Their mean serum I-PTH levels decreased significantly from 2 99 to 18 ng/l during the recovery phase (p < 0.05). Our study seems to suggest that the abnormal calcium metabolism in this unique patient g roup is in part caused by persistently decreased renal production of 1 ,25(OH)(2)D although increased monomeric CT levels were associated wit h hypocalcemia. However, whether or not a causal relationship exists m erits further investigation.